Steerable vertebroplasty system with cavity creation element

ABSTRACT

Methods and devices for augmenting bone, such as in performing vertebroplasty are disclosed. A bone cement injection needle is provided, having a laterally deflectable distal end. The distal end may be provided with a cavity creation element, such as an inflatable balloon. Systems are also disclosed, including the steerable injection needle, introducer and stylet. The system may additionally include a cement delivery gun, one-time use disposable cement cartridges and a cement mixing chamber. Methods are also disclosed.

This application claims the benefit under 35 U.S.C. §120 as acontinuation of U.S. patent application Ser. No. 12/029,428 filed onFeb. 11, 2008, which is in turn a continuation-in-part of U.S. patentapplication Ser. No. 11/941,764 filed on Nov. 16, 2007. The foregoingpriority applications are all incorporated by reference herein in theirentireties.

The present invention relates to bone augmentation devices andprocedures. In particular, the present invention relates to steerableinjection devices and systems for introducing conventional or novel bonecement formulations such as in performing vertebroplasty.

BACKGROUND OF THE INVENTION

According to the National Osteoporosis Foundation ten million Americanshave osteoporosis, and an estimated 34 million with low bone mass are atrisk of developing osteoporosis(http://www.nof.org/osteoporosis/diseasefacts.htm). Called the “silentdisease,” OSP develops slowly over a number of years without symptoms.Eighty percent of those affected are women, particularly petiteCaucasian and Asian women, although older men and women of all races andethnicities are at significant risk.

In the United States, 700,000 people are diagnosed with vertebralcompression fractures as a result of OSP each year. Morbidity associatedwith vertebral fractures includes severe back pain, loss of height anddeformity, all of which negatively affect quality of life.

Once microfracture of the vertebra begins, there is little the cliniciancan do except palliative medical treatment using analgesics, bed restand/or restriction of activity. With time, the microfractures widen atone level and without surgical intervention, the fractures cascadedownward with increasing kyphosis or “hunching” of the back. Once amechanical lesion develops, surgery is the only option. Vertebroplastyor kyphoplasty are the primary minimally-invasive surgical proceduresperformed for the treatment of compression-wedge fractures due to OSP.

Vertebroplasty stabilizes the collapsed vertebra by injectingpolymethylmethacrylate (PMMA) or a substantially equivalent bone cementinto cancellous bone space of the vertebrae. Besides providingstructural support to the vertebra, the exothermic reaction of PMMApolymerization is said to kill off the nociceptors or pain receptors inthe bone, although no proof of this hypothesis has been provided in theliterature. This procedure is typically performed as an outpatientprocedure and requires only a short-acting local or general anesthetic.Once the surgical area of the spine is anesthetized, the physicianinserts one or two needles through small skin incisions into either thepedicle (uni-transpedicular) or the pedicles of the vertebral body i.e.,bi-transpedicular. PMMA is injected through the needle and into thecancellous-bone space of the vertebra.

Kyphoplasty mirrors the vertebroplasty procedure but has the additionalstep of inserting and expanding a nylon balloon in the interior of thevertebral body. Expansion of the balloon under pressure reduces thecompression fracture and creates a cavity. After withdrawal of theballoon, PMMA is injected into the cavity to stabilize the reduction.The kyphoplasty procedure may restore the vertebral body height.Kyphoplasty is an in-patient surgery that requires hospitalization and ageneral anesthetic. Kyphon Inc. claims over 275,000 spinal fractureshave been treated using their PMMA derivative and their “balloon”kyphoplasty procedure worldwide (Sunnyvale, Calif., Sep. 5, 2006, (PRNEWSWIRE) Kyphon study 2006).

Bone cement for both vertebroplasty and kyphoplasty procedures currentlyemploy variations of standard PMMA in a powder and a methyl methacrylatemonomer liquid. When the powder and liquid monomer are mixed, anexothermic polymerization takes place resulting in the formation of a“dough-like” material, which is then inserted into the cancellous bonespace. The dough, when hardened, becomes either the reinforcingstructure or the grout between the bone and prosthesis.

The average clinical in vivo life of the PMMA grout is approximately 10years due to corrosion fatigue of either the bone-cement/prosthesisand/or the bone cement/bone interfaces. Jasty et al. (1991) showed thatin cemented total hip replacements: “Fractures in the cement mantleitself were found on cut sections around all prostheses which had beenin use for over three years.” Jasty et al. also noted: “In general,specimens less than 10 years in situ showed small incomplete fractureswhile the specimens in place more than 10 years all showed largecomplete cement mantle fractures.”

When an implant fails, a revision becomes mandatory. After removal ofthe cement and hardware, a cemented arthroplasty can be repeated ifenough cancellous bone matrix exists to grip the new PMMA.Alternatively, cement-less prosthesis can be installed. Such a revision,however, can only be applied to total joint replacement failures. Forvertebroplasty and/or kyphoplasty, a classical screw and plate internalfixation with autograft fusion is necessary.

Despite advances in the foregoing procedures, there remains a need forimproved bone cement delivery systems which enable rapid andcontrollable deployment of bone cement for the treatment of conditionssuch as vertebral compression fractures.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the presentinvention, a steerable vertebroplasty device having a cavity creationelement. The vertebroplasty device comprises an elongate tubular body,having a proximal end, a distal end, and a central lumen extendingtherethrough. A deflectable zone is provided on the distal end of thetubular body, for deflection through an angular range. A handle isprovided on the proximal end of the tubular body, having a deflectioncontrol thereon. A cavity creating element may be carried by thedeflectable zone. In one embodiment, the cavity creating element is aninflatable balloon, in communication with a proximal inflation port byway of an elongate inflation lumen extending throughout the length ofthe tubular body.

The deflection control may comprise a rotatable element, such as a knobrotatable about the longitudinal axis of the handle.

The distal end of the tubular body is provided with at least one exitport in communication with the central lumen. The exit port may open ina lateral direction, an axial direction, or along an inclined surfacepositioned distally of a transition point between the longitudinal sidewall of the tubular body and the distal end of the distal tip.

Further features and advantages of the present invention will becomeapparent to those of skill in the art in view of the detaileddescription of preferred embodiments which follows, when consideredtogether with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a steerable injection needle inaccordance with one aspect of the present invention.

FIG. 2 is a perspective view of an introducer in accordance with oneaspect of the present invention.

FIG. 3 is a perspective view of a stylet in accordance with one aspectof the present invention.

FIG. 4 is a side elevational view of the steerable injection needlemoveably coaxially disposed within the introducer, in a substantiallylinear configuration.

FIG. 5 is a side elevational view of the assembly of FIG. 4, showing thesteerable injection needle in a curved configuration.

FIG. 6 is a side elevational schematic view of another steerableinjection needle in accordance with the present invention.

FIG. 7A is a schematic view of a distal portion of the steerable needleof FIG. 6, shown in a linear configuration.

FIG. 7B is a schematic view as in FIG. 7A, following proximal retractionof a pull wire to laterally deflect the distal end.

FIG. 8 is a schematic view of a distal portion of a steerable needle,having a side port.

FIG. 9A is a schematic view of a distal portion of a steerable needle,positioned within an outer sheath.

FIG. 9B is an illustration as in FIG. 9A, with the distal sheathpartially proximally retracted.

FIG. 9C is an illustration as in FIG. 9B, with the outer sheathproximally retracted a sufficient distance to fully expose thedeflection zone.

FIGS. 10A-10C illustrate various aspects of an alternative deflectableneedle in accordance with the present invention.

FIGS. 11A through 11C illustrate various aspects of a furtherdeflectable needle design in accordance with the present invention.

FIGS. 12 and 13 illustrate a further variation of the deflectable needledesign in accordance with the present invention.

FIG. 14 is a side elevational cross section through the proximal handleof the deflectable needle illustrated in FIG. 13.

FIG. 15 is a cross sectional detail view of the distal tip of thesteerable needle illustrated in FIG. 13.

FIGS. 15A through 15H illustrate various views of alternative distal tipdesigns.

FIGS. 16A and 16B are schematic illustrations of the distal end of asteerable injection device in accordance with the present invention,having a cavity creating element thereon.

FIGS. 16C and 16D are alternative cross sectional views taken along theline 16C-16C in FIG. 16A, showing different inflation lumenconfigurations.

FIGS. 17A and 17B illustrate an alternative steerable injection devicehaving a cavity creation element thereon.

FIGS. 18A and 18B are schematic views of a bone cement delivery systemin accordance with the present invention.

FIGS. 19A through 19F show stages in the method of accomplishingvertebroplasty in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides improved delivery systems for delivery ofa bone cement or bone cement composite for the treatment of vertebralcompression fractures due to osteoporosis (OSP), osteo-trauma, andbenign or malignant lesions such as metastatic cancers and myeloma, andassociated access and deployment tools and procedures.

The primary materials in the preferred bone cement composite are methylmethacrylate and inorganic cancellous and/or cortical bone chips orparticles. Suitable inorganic bone chips or particles are sold byAllosource, Osteotech and LifeNet (K053098); all have been cleared formarketing by FDA The preferred bone cement also may contain theadditives: barium sulfate for radio-opacity, benzoyl peroxide as aninitiator, N,N-dimethyl-p-toluidine as a promoter and hydroquinone as astabilizer. Other details of bone cements and systems are disclosed inU.S. patent application Ser. No. 11/626,336, filed Jan. 23, 2007, thedisclosure of which is hereby incorporated in its entirety herein byreference.

One preferred bone cement implant procedure involves a two-stepinjection process with two different concentrations of the bone particleimpregnated cement. To facilitate the implant procedure the bone cementmaterials are packaged in separate cartridges containing specific bonecement and inorganic bone particle concentrations for each step. Tables1 and 2, infra, list one example of the respective contents andconcentrations in Cartridges 1A and 1B for the first injection step, andCartridges 2A and 2B for the second injection step.

The bone cement delivery system generally includes at least three maincomponents: 1) stylet; 2) introducer cannula; and 3) steerable injectionneedle. See FIGS. 1-3. Packaged with the system or packaged separatelyis a cement dispensing pump. The complete system also preferablyincludes at least one cement cartridge having at least two chamberstherein, and a spiral mixing nozzle.

The stylet is used to perforate a hole into the pedicle of the vertebrato gain access to the interior of the vertebral body.

The introducer cannula is used for bone access and as a guide for thesteerable injection needle. The introducer cannula is sized to allowphysicians to perform vertebroplasty or kyphoplasty on vertebrae withsmall pedicles such as the thoracic vertebra T5 as well as largervertebrae. In addition, this system is designed for uni-transpedicularaccess and/or bi-pedicular access.

Once bone access has been achieved, the steerable injection needle canbe inserted through the introducer cannula into the vertebra. The entireinterior vertebral body may be accessed using the steerable injectionneedle. The distal end of the needle can be manually shaped to anydesired radius within the product specifications. The radius is adjustedby means of a knob on the proximal end of the device.

The hand-held cement dispensing pump may be attached to the steerableinjection needle by a slip-ring leer fitting. The pre-filled 2-chamberedcartridges (1A and 1B, and 2A and 2B) are loaded into the dispensingpump. As the handle of the dispensing pump is squeezed, each pistonpushes the cartridge material into the spiral mixing tube. The materialsare mixed in the spiral mixing nozzle prior to entering the steerableinjection needle. The ratio of diameters of the cartridge chambersdetermines the mixing ratio for achieving the desired viscosity.

The bone cement implant procedures described herein use establishedvertebroplasty and kyphoplasty surgical procedures to stabilize thecollapsed vertebra by injecting bone cement into cancellous bone.

The preferred procedure is designed for uni-transpedicular access andmay be accomplished under either a local anesthetic or short-durationgeneral anesthetic. Once the area of the spine is anesthetized, anincision is made and the stylet is used to perforate the vertebralpedicle and gain access to the interior of the vertebral body. Theintroducer cannula is then inserted and acts as a guide for thesteerable injection needle.

Injection of the preferred bone cement involves a two-step procedure.The pre-filled Cartridges 1A and 1B are loaded into the dispensing pump.As the dispensing pump handle is squeezed, each piston pushes materialinto the spiral mixing tube. The diameter of each chamber may beutilized to determine the mixing ratio for achieving the desiredviscosity.

The first step involves injecting a small quantity of PMMA with morethan about 35%, e.g., 60% inorganic bone particles, onto the outerperiphery of the cancellous bone matrix, i.e., next to the inner wall ofthe cortical bone of the vertebral body. The cement composite isdesigned to harden relatively quickly, forming a firm but still pliableshell. This shell is intended to prevent bone marrow/PMMA content frombeing ejected through any venules or micro-fractures in the vertebralbody wall. The second step of the procedure involves a second injectionof PMMA with an approximately 30% inorganic bone particles to stabilizethe remainder of the weakened, compressed cancellous bone.

Alternatively, the steerable needle disclosed herein and discussed ingreater detail below, can be used in conventional vertebroplastyprocedures, using a single step bone cement injection.

Injection control for the first and second steps is provided by a 2 mmID flexible injection needle, which is coupled to the hand operated bonecement injection pump. The 60% (>35%) and 30% ratio of inorganic boneparticle to PMMA concentrations may be controlled by the pre-filledcartridge sets 1A and 1B, and 2A and 2B. At all times, the amount of theinjectate is under the direct control of the surgeon or interventionradiologist and visualized by fluoroscopy. The introducer cannula isslowly withdrawn from the cancellous space as the second injection ofbone cement begins to harden, thus preventing bone marrow/PMMA contentfrom exiting the vertebral body. The procedure concludes with closure ofthe surgical incision with bone filler. In vitro and in vivo studieshave shown that the 60% (>35%) bone-particle impregnated bone cementhardens in 2-3 minutes and 30% bone-particle impregnated bone cementhardens between 4 to 10 minutes.

Details of the system components will be discussed below.

There is provided in accordance with the present invention a steerableinjection device that can be used to introduce any of a variety ofmaterials or devices for diagnostic or therapeutic purposes. In oneembodiment, the system is used to inject bone cement, e.g., PMMA or anyof the bone cement compositions disclosed elsewhere herein. Theinjection system most preferably includes a tubular body with asteerable (i.e., deflectable) distal portion for introducing bone cementinto various locations displaced laterally from the longitudinal axis ofthe device within a vertebral body during a vertebroplasty procedure.

Referring to FIG. 1, there is illustrated a side perspective view of asteerable injection needle 10 in accordance with one aspect of thepresent invention. The steerable injection needle 10 comprises anelongate tubular body 12 having a proximal end 14 and a distal end 16.The proximal end 14 is provided with a handle or manifold 18, adapted toremain outside of the patient and enable introduction and/or aspirationof bone cement or other media, and control of the distal end as will bedescribed herein. In general, manifold 18 is provided with at least oneinjection port 20, which is in fluid communication with a central lumen(not illustrated) extending through tubular body 12 to at least onedistal exit port 22.

The manifold 18 is additionally provided with a control 26 such as arotatable knob, slider, or other moveable control, for controllablydeflecting a deflection zone 24 on the distal end 16 of the tubular body12. As is described elsewhere herein, the deflection zone 24 may beadvanced from a relatively linear configuration as illustrated in FIG. 1to a deflected configuration throughout an angular range of motion.

Referring to FIG. 2, there is illustrated an elongate tubular introducer30, having a proximal end 32, a distal end 34 and an elongate tubularbody 36 extending therebetween. A central lumen 38 (not shown) extendsbetween a proximal access port 40 and a distal access port 42.

The central lumen 38 has an inside diameter which is adapted toslideably axially receive the steerable injection needle 10therethrough. This enables placement of the distal end 34 adjacent atreatment site within the body, to establish an access pathway fromoutside of the body to the treatment site. As will be appreciated bythose of skill in the art, the introducer 30 enables procedures deepwithin the body such as within the spine, through a minimally invasiveand/or percutaneous access. The steerable injection needle 10 and/orother procedure tools may be introduced into port 40, through lumen 38and out of port 42 to reach the treatment site.

The proximal end 32 of introducer 30 may be provided with a handle 44for manipulation during the procedure. Handle 44 may be configured inany of a variety of ways, such as having a frame 46 with at least afirst aperture 48 and a second aperture 50 to facilitate grasping by theclinician.

Referring to FIG. 3, there is illustrated a perspective view of stylet60. Stylet 60 comprises a proximal end 62, a distal end 64 and anelongate body 66 extending therebetween. The proximal end 62 may beprovided with a stop 68 such as a grasping block, manifold or otherstructure, to facilitate manipulation by the clinician. In theillustrated embodiment, the block 68 is configured to nest within arecess 70 on the proximal end of the introducer 30.

As will be appreciated by those of skill in the art, the stylet 60 hasan outside diameter which is adapted to coaxially slide within thecentral lumen on introducer 30. When block 68 is nested within recess70, a distal end 64 of stylet 60 is exposed beyond the distal end 34 ofintroducer 30. The distal end 64 of stylet 60 may be provided with apointed tip 72, such as for anchoring into the surface of a bone.

Referring to FIG. 4, there is illustrated a side elevational view of anassembly in accordance with the present invention in which a steerableinjection needle 10 is coaxially positioned within an introducer 30. Theintroducer 30 is axially moveably carried on the steerable injectionneedle 10. In the illustration of FIG. 4, the introducer 30 isillustrated in a distal position such that it covers at least a portionof the deflection zone 24 on injection needle 10.

FIG. 5 illustrates an assembly as in FIG. 4, in which the introducer 30has been proximally retracted along the injection needle 10 to fullyexpose the deflection zone 24 on injection needle 10. In addition, thecontrol 26 has been manipulated to deflect the deflection zone 24through an angle of approximately 90°. Additional details of thesteerable needle will be discussed below.

FIG. 6 illustrates a schematic perspective view of an alternatesteerable vertebroplasty injector, according to one embodiment of theinvention. The steerable injector 700 includes a body or shaft portion702 that is preferably elongate and tubular, input port 704, adjustmentcontrol 706, and handle portion 708. The elongate shaft 702 preferablyhas a first proximal portion 710 and a second distal portion 712 whichmerge at a transition point 714. Shaft 702 may be made of stainlesssteel, such as 304 stainless steel, Nitinol, Elgiloy, or otherappropriate material. Alternatively, the tubular body 702 may beextruded from any of a variety of polymers well known in the catheterarts, such as PEEK, PEBAX, nylon and various polyethylenes. Extrudedtubular bodies 702 may be reinforced using metal or polymeric spiralwrapping or braided wall patterns, as is known in the art.

The shaft 702 defines at least one lumen therethrough that is preferablyconfigured to carry a flowable bone cement prior to hardening. Proximalportion 710 of shaft 702 is preferably relatively rigid, havingsufficient column strength to push through cancellous bone. Distalportion 712 of shaft 702 is preferably flexible and/or deflectable andreversibly actuatable between a relatively straight configuration andone or more deflected configurations or curved configurations asillustrated, for example, in FIG. 5, as will be described in greaterdetail below. The distal portion 712 of shaft 702 may include aplurality of transverse slots 718 that extend partiallycircumferentially around the distal portion 712 of the shaft 702 toprovide a plurality of flexion joints to facilitate bending.

Input port 704 may be provided with a Luer lock connector although awide variety of other connector configurations, e.g., hose barb or slipfit connectors can also be used. Lumen 705 of input port 704 is fluidlyconnected to central lumen 720 of shaft 702 such that material can flowfrom a source, through input port 704 into central lumen 720 of theshaft 702 and out the open distal end or out of a side opening on distalportion 712. Input port 704 is preferably at least about 20 gauge andmay be at least about 18, 16, 14, or 12 gauge or larger in diameter.

Input port 704 advantageously allows for releasable connection of thesteerable injection device 700 to a source of hardenable media, such asa bone cement mixing device described herein. In some embodiments, aplurality of input ports 704, such as 2, 3, 4, or more ports arepresent, for example, for irrigation, aspiration, introduction ofmedication, hardenable media precursors, hardenable media components,catalysts or as a port for other tools, such as a light source, cautery,cutting tool, visualization devices, or the like. A first and secondinput port may be provided, for simultaneous introduction of first andsecond bone cement components such as from a dual chamber syringe orother dispenser. A mixing chamber may be provided within the injectiondevice 700, such as within the proximal handle, or within the tubularshaft 702

A variety of adjustment controls 706 may be used with the steerableinjection system, for actuating the curvature of the distal portion 712of the shaft 702. Preferably, the adjustment control 706 advantageouslyallows for one-handed operation by a physician. In one embodiment, theadjustment control 706 is a rotatable member, such as a thumb wheel ordial. The dial can be operably connected to a proximal end of an axiallymovable actuator such as pull wire 724. See FIG. 7A. When the dial isrotated in a first direction, a proximally directed tension force isexerted on the pull wire 724, actively changing the curvature of thedistal portion 712 of the shaft 702 as desired. The degree of deflectioncan be observed fluoroscopically, and/or by printed or other indiciumassociated with the control 706. Alternative controls include rotatableknobs, slider switches, compression grips, triggers such as on a gungrip handle, or other depending upon the desired functionality.

In some embodiments, the adjustment control 706 allows for continuousadjustment of the curvature of the distal portion 712 of shaft 702throughout a working range. In other embodiments, the adjustment controlis configured for discontinuous (i.e., stepwise) adjustment, e.g., via aratcheting mechanism, preset slots, deflecting stops, a rack and pinionsystem with stops, ratcheting band (adjustable zip-tie), adjustable cam,or a rotating dial of spring loaded stops. In still other embodiments,the adjustment control 706 may include an automated mechanism, such as amotor or hydraulic system to facilitate adjustment.

The adjustment control may be configured to allow deflection of thedistal portion 712 through a range of angular deviations from 0 degrees(i.e., linear) to at least about 15°, and often at least about 25°, 35°,60°, 90°, 120°, 150°, or more degrees from linear.

In some embodiments, the length X of the flexible distal portion 712 ofshaft 702 is at least about 10%, in some embodiments at least about 15%,25%, 35%, 45%, or more of the length Y of the entire shaft 702 foroptimal delivery of bone cement into a vertebral body. One of ordinaryskill in the art will recognize that the ratio of lengths X:Y can varydepending on desired clinical application. In some embodiments, themaximum working length of needle 702 is no more than about 15″, 10″, 8″,7″, 6″, or less depending upon the target and access pathway. In oneembodiment, when the working length of needle 702 is no more than about8″, the adjustable distal portion 712 of shaft has a length of at leastabout 1″ and preferably at least about 1.5″ or 2″.

FIGS. 7A-B are schematic perspective views of a distal portion of shaft702 of a steerable vertebroplasty injector, according to one embodimentof the invention. Shown is the preferably rigid proximal portion 710 anddeflectable distal portion 712. The distal portion 712 of shaft 702includes a plurality of transverse slots 718 that extend partiallycircumferentially around the distal portion 712 of the shaft 702,leaving a relatively axially non-compressible spine 719 in the form ofthe unslotted portion of the tubular wall.

In some embodiments, the slots 718 can be machined or laser cut out ofthe tube stock that becomes shaft 702, and each slot may have a linear,chevron or other shape. In other embodiments, the distal portion 712 ofshaft 702 may be created from an elongate coil rather than a continuoustube.

Slots 718 provide small compression hinge joints to assist in thereversible deflection of distal portion 712 of shaft 702 between arelatively straightened configuration and one or more curvedconfigurations. One of ordinary skill in the art will appreciate thatadjusting the size, shape, and/or spacing of the slots 718 can impartvarious constraints on the radius of curvature and/or limits ofdeflection for a selected portion of the distal portion 712 of shaft702. For example, the distal portion 712 of shaft 702 may be configuredto assume a second, fully deflected shape with a relatively constantradius of curvature throughout its length. In other embodiments, thedistal portion 712 may assume a progressive curve shape with a variableradius of curvature which may, for example, have a decreasing radiusdistally. In some embodiments, the distal portion may be laterallydisplaced through an arc having a radius of at least about 0.5″, 0.75″,1.0″, 1.25″, or 1.5″ minimum radius (fully deflected) to ∞ (straight) tooptimize delivery of bone cement within a vertebral body. Wall patternsand deflection systems for bendable slotted tubes are disclosed, forexample, in U.S. Patent Publication No. 2005/0060030 A1 to Lashinski etal., the disclosure of which is incorporated in its entirety byreference herein.

Still referring to FIGS. 7A-B, a pull wire 724 resides within the lumen720 of shaft 702. The distal end 722 of the pull wire 724 is preferablyoperably attached, such as by adhesive, welding, soldering, crimping orthe like, to an inner side wall of the distal portion 712 of the shaft702. Preferably, the attachment point will be approximately 180° offsetfrom the center of the axially extending spine 719. Proximal portion ofpull wire 724 is preferably operably attached to adjustment control 706.The adjustment control 706 may be configured to provide an axial pullingforce in the proximal direction toward the proximal end of pull wire724. This in turn exerts a proximal traction on the distal portion 712of shaft 702 operably attached to distal end 722 of pull wire 724. Theslotted side of the tubular body shortens under compression, while thespine side 719 retains its axial length causing the distal portion 712of shaft 702 to assume a relatively curved or deflected configuration.In some embodiments, a plurality of pull wires, such as two, three,four, or more pull wires 724 may be present within the lumen 720 withdistal points of attachment spaced axially apart to allow the distalportion 712 of shaft 702 to move through compound bending curvesdepending on the desired bending characteristic. Distal axial advance ofthe actuator will cause a deflection in an opposite direction, byincreasing the width of the slots 718.

A distal opening 728 is provided on shaft 702 in communication withcentral lumen 720 to permit expression of material, such as bone cement,from the injector 700. Some embodiments may include a filter such asmesh 812. Mesh structure 812 can advantageously control cement output bycontrolling bubbles and/or preventing undesired large or unwieldyaggregations of bone cement from being released at one location and thuspromote a more even distribution of bone cement within the vertebralbody. The mesh 812 may be created by a laser-cut cris-crossing patternwithin distal end as shown, or can alternatively be separately formedand adhered, welded, or soldered on to the distal opening 728. Referringto FIG. 8, the distal shaft portion 712 may also include an end cap 730or other structure for occluding central lumen 720, and a distal opening728 on the sidewall of shaft 702.

In some embodiments, the distal shaft 712 can generate a lateral forceof at least about 0.125 pounds, 0.25 pounds, 0.5 pounds, 1 pound, 1.5pounds, 2 pounds, 3 pounds, 4 pounds, 5 pounds, 6 pounds, 7 pounds, 8pounds, 9 pounds, 10 pounds, or more by activating control 706. This canbe advantageous to ensure that the distal portion 712 is sufficientlynavigable laterally through cancellous bone to distribute cement to thedesired locations. In some embodiments, the distal shaft 712 cangenerate a lateral force of at least about 0.125 pounds but no more thanabout 10 pounds; at least about 0.25 pounds but no more than about 7pounds; or at least about 0.5 pounds but no more than about 5 pounds.

In some embodiments, the distal portion 712 of shaft 702 (or end cap730) has visible indicia, such as, for example, a marker visible via oneor more imaging techniques such as fluoroscopy, ultrasound, CT, or MRI.

FIGS. 9A-C illustrate in schematic cross-section another embodiment of adistal portion 734 of a steerable injection device 740. The tubularshaft 736 can include a distal portion 734 made of or containing, forexample, a shape memory material that is biased into an arc when in anunconstrained configuration. Some materials that can be used for thedistal curved portion 734 include Nitinol, Elgiloy, stainless steel, ora shape memory polymer. A proximal portion 732 of the shaft 736 ispreferably relatively straight as shown. Also shown is end cap 730,distal lateral opening 728 and mesh 812.

The distal curved portion 734 may be configured to be axially movablyreceived within an outer tubular sheath 738. The sheath 738 ispreferably configured to have sufficient rigidity and radial strength tomaintain the curved distal portion 734 of shaft 732 in a relativelystraightened configuration while the outer tubular sheath 738 coaxiallycovers the curved distal portion 734. Sheath 738 can be made of, forexample, a metal such as stainless steel or various polymers known inthe catheter arts. Axial proximal withdrawal of the sheath 738 withrespect to tubular shaft 736 will expose an unconstrained portion of theshape memory distal end 734 which will revert to its unstressed arcuateconfiguration. Retraction of the sheath 738 may be accomplished bymanual retraction by an operator at the proximal end, retraction of apull wire attached to a distal portion of the sheath 738, or other waysas known in the art. The straightening function of the outer sheath 738may alternatively be accomplished using an internal stiffening wire,which is axially movably positionable within a lumen extending throughthe tubular shaft 736. The length, specific curvature, and other detailsof the distal end may be as described elsewhere herein.

In another embodiment, as shown in FIGS. 10A-C, tubular shaft 802 of asteerable vertebroplasty injector may be generally substantiallystraight throughout its length in its unstressed state, or have alaterally biased distal end. A distally facing or side facing opening810 is provided for the release of a material, such as bone cement. Inthis embodiment, introducer 800 includes an elongate tubular body 801with a lumen 805 therethrough configured to receive the tubular shaft(also referred to as a needle) 802. Introducer 800 can be made of anyappropriate material, such as, stainless steel and others disclosedelsewhere herein. Needle 802 may be made of a shape memory material,such as nitinol, with superelastic properties, and has an outsidediameter within the range of between about 1 to about 3 mm, about1.5-2.5 mm, or about 2.1 mm in some embodiments.

Introducer 800 includes a needle-redirecting element 804 such as aninclined surface near its distal end. Needle-redirecting element 804 canbe, for example, a laser-cut tang or a plug having a proximal surfaceconfigured such that when needle 802 is advanced distally intointroducer 800 and comes in contact with the needle-redirecting element804, a distal portion 814 of needle 802 is redirected out an exit port806 of introducer 800 at an angle 808, while proximal portion 816 ofneedle 802 remains in a relatively straightened configuration, as shownin FIG. 10B. Bone cement can then be ejected from distal opening 810 onthe end or side of needle 802 within bone 1000. Distal opening 810 maybe present at the distal tip of the needle 802 (coaxial with the longaxis of the needle 802) or alternatively located on a distal radial wallof needle 802 as shown in FIG. 10C. In some embodiments, the angle 808is at least about 15 degrees and may be at least about 30, 45, 60, 90,105 degrees or more with respect to the long axis of the introducer 800.

The illustrated embodiment of FIGS. 10A-C and other embodimentsdisclosed herein are steerable through multiple degrees of freedom todistribute bone cement to any area within a vertebral body. For example,the introducer 800 and needle 802 can both rotate about theirlongitudinal axes with respect to each other, and needle 802 can movecoaxially with respect to the introducer 800, allowing an operator toactuate the injection system three dimensionally. The distal portion 814of needle 802 can be deflected to a position that is angularly displacedfrom the long axis of proximal portion 816 of needle without requiring adiscrete curved distal needle portion as shown in other embodimentsherein.

FIGS. 11A-C illustrate another embodiment of a steerable vertebroplastyinjector. FIG. 11A schematically shows handle portion 708, adjustmentcontrol 706, and elongate needle shaft 702, including proximal portion710, distal portion 712, and transition point 714. FIG. 11B is avertical cross-section through line A-A of FIG. 11A, and showsadjustment control 706 operably connected to pull wire 724 such asthrough a threaded engagement. Also shown is input port 704, andproximal portion 710 and distal portion 712 of needle shaft 702. FIG.11C illustrates a cross-sectional view of distal portion 712 of shaft702. The distal end 722 of pull wire 724 is attached at an attachmentpoint 723 to the distal portion 712 of shaft 702. Proximal retraction onpullwire 724 will collapse transverse slots 718 and deflect the injectoras has been discussed. Also shown is an inner tubular sleeve 709, whichcan be advantageous to facilitate negotiation of objects or media suchas bone cement, through the central lumen of the needle shaft 702.

The interior sleeve 709 is preferably in the form of a continuous,tubular flexible material, such as nylon or polyethylene. In anembodiment in which the needle 702 has an outside diameter of 0.095inches (0.093 inch coil with a 0.001 inch thick outer sleeve) and aninside diameter of 0.077 inches, the interior tubular sleeve 709 mayhave an exterior diameter in the area of about 0.074 inches and aninterior diameter in the area of about 0.069 inches. The use of thisthin walled tube 705 on the inside of the needle shaft 702 isparticularly useful for guiding a fiber through the needle shaft 702.The interior tube 705 described above is additionally preferablyfluid-tight, and can be used to either protect the implementstransmitted therethrough from moisture, or can be used to transmit bonecement through the steerable needle.

In some embodiments, an outer tubular coating or sleeve (not shown) isprovided for surrounding the steerable needle shaft at least partiallythroughout the distal end of the needle. The outer tubular sleeve may beprovided in accordance with techniques known in the art and, in oneembodiment, is a thin wall polyester (e.g., ABS) heat shrink tubing suchas that available from Advanced Polymers, Inc. in Salem, N.H. Such heatshrink tubings have a wall thickness of as little as about 0.0002 inchesand tube diameter as little as about 0.010 inches. The outer tubularsleeve enhances the structural integrity of the needle, and alsoprovides a fluid seal and improved lubricity at the distal end overembodiments with distal joints 718. Furthermore, the outer tubularsleeve tends to prevent the device from collapsing under a proximalforce on a pull wire. The sleeve also improves pushability of thetubular members, and improves torque transmission.

In other embodiments, instead of a slotted tube, the needle shaft of avertebroplasty injection system may include a metal or polymeric coil.Steerable helical coil-type devices are described, for example, in U.S.Pat. No. 5,378,234 or 5,480,382 to Hammerslag et al., which are bothincorporated by reference herein in their entirety.

An interior tubular sleeve (not illustrated) may be provided tofacilitate flow of media through the central lumen as describedelsewhere in the application. In some embodiments, a heat-shrink outertubular sleeve as described elsewhere in the application is alsoprovided to enhance the structural integrity of the sheath, provide afluid seal across the chevrons or slots, as well as improve lubricity.

The steerable injection needle (also referred to as the injection shaft)may have an outside diameter of between about 8 to 24 gauge, morepreferably between about 10 to 18 gauge, e.g., 12 gauge, 13 gauge(0.095″ or 2.41 mm), 14 gauge, 15 gauge, or 16 gauge. In someembodiments, the inside diameter (luminal diameter) of the injectionneedle is between about 9 to 26 gauge, more preferably between about 11to 19 gauge, e.g., 13 gauge, 14 gauge, 15 gauge, 16 gauge, or 17 gauge.In some embodiments, the inside diameter of the injection needle is nomore than about 4 gauge, 3 gauge, 2 gauge, or 1 gauge smaller than theoutside diameter of the injection needle.

The inside luminal diameter of all of the embodiments disclosed hereinis preferably optimized to allow a minimal exterior delivery profilewhile maximizing the amount of bone cement that can be carried by theneedle. In one embodiment, the outside diameter of the injection needleis 13 gauge (0.095″ or 2.41 mm) with a 0.077″ (1.96 mm) lumen. In someembodiments, the percentage of the inside diameter with respect to theoutside diameter of the injection needle is at least about 60%, 65%,70%, 75%, 80%, 85%, or more.

Referring to FIGS. 12 and 13, there is illustrated a modification of thesteerable injection needle 10, in accordance with the present invention.The injection needle 10 comprises an elongate tubular shaft 702,extending between a proximal portion 710 and a distal portion 712. Theproximal portion 710 is carried by a proximal handle 708, which includesa deflection control 706 such as a rotatable knob or wheel. Rotation ofthe control 706 causes a lateral deflection or curvature of the distalsteering region 24 as has been discussed.

Input port 704 is in fluid communication with a distal opening 728 on adistal tip 730, by way of an elongate central lumen 720. Input port 704may be provided with any of a variety of releasable connectors, such asa luer or other threaded or mechanically interlocking connector known inthe art. Bone cement or other media advanced through lumen 720 underpressure may be prevented from escaping through the plurality of slots718 in the steering region 24 by the provision of a thin flexibletubular membrane carried either by the outside of tubular shaft 702, oron the interior surface defining central lumen 720.

Referring to FIG. 14, the handle 708 is provided with an axiallyoriented central bore 732 having a first, female thread 733 thereon. Aslider 734 having a second complementary male thread 735, is threadablyengaged with the central bore 732. Rotation of the knob 706 relativelyto the slider 734 thus causes the slider 734 to distally advance orproximally retract in an axial direction with respect to the handle 708.The slider 734 is mechanically linked to the pull wire 724, such as bythe use of one or more set screws or other fastener 740.

Slider 734 is provided with at least one axially extending keyway orspline 742 for slideably engaging a slide dowel pin 744 linked to thehandle 708. This allows rotation of the rotatable control 706, yetprevents rotation of the slider 734 while permitting axial reciprocalmovement of the slider 734 as will be apparent to those of skill in theart. One or more actuating knob dowel pins 746 permits rotation of therotatable control 706 with respect to the handle 708 but prevents axialmovement of the rotatable control 706 with respect to the handle 708.

Referring to FIG. 15, the distal end of the shaft 702 may be providedwith any of a variety of distal opening 728 orientations or distal tip730 designs, depending upon the desired functionality. In theillustrated embodiment, the distal tip 730 is provided with an annularflange 748 which may be slip fit into the distal end of the tubular body702, to facilitate attachment. The attachment of the distal tip 730 maybe further secured by welding, crimping, adhesives, or other bondingtechnique.

In general, the distal tip 730 includes a proximal opening 750 forreceiving media from the central lumen 720, and advancing media throughdistal opening 728. Distal opening 728 may be provided on a distallyfacing surface, on a laterally facing surface, or on an inclined surfaceof the distal tip 730.

Referring to FIGS. 15A and 15B, there is illustrated a distal tip 30having a single inclined opening 728 thereon. In any of the designsdisclosed herein, one or two or three or four or more distal ports 728may be provided, depending upon the desired clinical performance. In theillustrated embodiment, the distal tip includes a rounded distal end 750which transitions either smoothly or through an angular interface withan inclined portion 752. The distal opening 728 is positioned distallyof a transition 754 at the proximal limit of the inclined surface 752.This configuration enables the distal opening 728 to have a distalaxially facing component, as compared to an embodiment having a sidewall opening. See, for example, FIG. 8.

Referring to FIG. 15B, the tip 730 can be considered to have a centrallongitudinal axis 770. The aperture 728 may be considered as residing onan aperture plane 772, which intersects the distal most limit and theproximal most limit of the aperture 728. Aperture plane 772 intersectsthe longitudinal axis at an angle θ. In an embodiment having a side wallaperture, the aperture plane 772 and longitudinal axis 770 would beparallel. In an embodiment having a completely distally facing aperture,the aperture plane 772 would intersect the longitudinal axis 770 at anangle of 90°.

In the illustrated embodiment, the inclined aperture 728 is defined byan aperture plane 772 intersecting the longitudinal axis 770 at an angleθ which is at least about 5°, often at least about 15°, and in manyembodiments, at least about 25° or more. Intersection angles within therange of from about 15° to about 45° may often be used, depending uponthe desired clinical performance.

Referring to FIGS. 15C and 15D, an alternate distal tip 730 isillustrated. In this configuration, the distal opening 728 is in theform of a sculpted recess 756 extending axially in alignment with atleast a portion of the central lumen 720. Sculpted recess 756 may beformed in any of a variety of ways, such as by molding, or by drillingan axial bore in an axial direction with respect to the tip 730. Thesculpted recess 756 cooperates with the tubular body 702, as mounted, toprovide a distal opening 728 having an inclined aspect as well as anaxially distally facing aspect with respect to the longitudinal axis ofthe steerable needle.

Referring to FIGS. 15E and 15F, there is illustrated a distal tip 730having a plurality of distally facing apertures 728. In the illustratedembodiment, four distal apertures are provided. The distal apertures 728may be provided on the rounded distal end 750, or on an inclined surface752 as has been discussed.

Referring to FIGS. 15G and 15H, there is illustrated an alternativedistal tip 730. In this configuration, an opening 728 is oriented in adistally facing direction with respect to the longitudinal axis of theneedle. The distal opening of the central lumen is covered by at leastone, preferably two, and, as illustrated, four leaflets 758 to provide acollet like configuration. Each of the adjacent leaflets 758 isseparated by a slot 760 and is provided with a living hinge or otherflexible zone 762.

In use, the distal tip 730 may be distally advanced through soft tissue,cortical or cancellous bone, with the distal opening 728 beingmaintained in a closed orientation. Following appropriate positioning ofthe distal tip 30, the introduction of bone cement or other media underpressure through the central lumen 720 forces the distal opening 728open by radially outwardly inclining each leaflet 758 about its flectionpoint 762. This configuration enables introduction of the needle without“coring” or occluding with bone or other tissue, while still permittinginjection of bone cement or other media in a distal direction.

Any of the forgoing or other tip configurations may be separately formedand secured to the distal end of the tubular body 702, or may bemachined, molded or otherwise formed integrally with the tube 702.

Alternatively, a distal opening aperture may be occluded by a blunt plugor cap, which prevents coring during distal advance of the device. Oncepositioned as desired, the distal cap may be pushed off of the distalend of the injector such as under the pressure of injected bone cement.The deployable cap may take any of a variety of forms depending upon theinjector design. For example, it may be configured as illustrated inFIG. 15A, only without the aperture 728. The flange 748 is slip fitwithin the distal end of the injector body, and retained only byfriction, or by a mild bond which is sufficient to retain the cap 730during manipulation of the injector, but insufficient to resist theforce of injected bone cement. The deployable cap 730 may be made fromany of a variety of materials, such as stainless steel, Nitinol, orother implantable metals; any of a wide variety of implantable polymerssuch as PEEK, nylon, PTFE; or of bone cement such as PMMA.Alternatively, any of a variety of bioabsorbable polymers may beutilized to form the deployable cap 730, including blends and polymersin the PLA-PGLA absorbable polymer families.

As a further alternative, coring during insertion of an injector havinga distal opening may be prevented by positioning a removable obturatorin the distal opening. The obturator comprises an elongate body,extending from a proximal end throughout the length of the injector to ablunt distal tip. The obturator is advanced axially in a distaldirection through the central lumen, until the distal tip of theobturator extends slightly distally of the distal opening in theinjector. This provides a blunt atraumatic tip for distal advance of theinjector through tissue. Following positioning of the injector, theobturator may be proximally withdrawn from the central lumen, anddiscarded. The obturator may be provided with any of a variety ofstructures for securing the obturator within the central lumen duringthe insertion step, such as a proximal cap for threadably engaging acomplementary leer connector on the proximal opening of the centrallumen.

In accordance with another aspect of the present invention, there isprovided a combination device in which a steerable injector isadditionally provided with a cavity formation element. Thus, the singledevice may be advanced into a treatment site within a bone, expanded toform a cavity, and used to infuse bone cement or other media into thecavity. Either or both of the expansion step and the infusion step maybe accomplished following or with deflection of the distal portion ofthe injector.

Referring to FIGS. 16A and 16B, the distal portion 302 of a steerableinjector 300 having a cavity formation element 320 thereon isschematically illustrated. The steerable injector 300 includes arelatively rigid proximal section 304 and a deflectable section 306 ashas been discussed elsewhere herein. The lateral flexibility of distalsection 306 may be accomplished in any of a variety of ways, such as bythe provision of a plurality of transverse chevrons or slots 308. Slots308 may be machined or laser cut into appropriate tube stock, such asstainless steel or any of a variety of rigid polymers.

The slots 308 oppose a column strength element such as an axiallyextending spine 310, for resisting axial elongation or compression ofthe device. A pull wire 312 axially moveably extends throughout thelength of the tubular body, and is secured with respect to the tubularbody distally of the transverse slots 308. The proximal end of the pullwire is operatively connected to a control on a proximal handpiece ormanifold. The control may be any of a variety of structures, such as alever, trigger, slider switch or rotatable thumb wheel or control knob.Axial proximal traction (or distal advance) of the pull wire 312 withrespect to the tubular body causes a lateral deflection of the distalsteering section 306, by axial compression or expansion of thetransverse slots 308 relative to the spine 310.

A distal aperture 314 is in communication via a central lumen 316 withthe proximal end of the steerable injector 300. Any of a variety of tipconfigurations may be used such as those disclosed elsewhere herein. Theproximal end of the central lumen 316 may be provided with a leerconnector, or other connection port to enable connection to a source ofmedia such as bone cement to be infused. In the illustrated embodiment,the aperture 314 faces distally from the steerable injector 302,although other exit angles may be used as will be discussed below.

The steerable injector 300 is optionally provided with a cavity formingelement 320, such as an inflatable balloon 322. In the illustratedembodiment, the inflatable balloon 322 is positioned in the vicinity ofthe steerable distal section 306. Preferably, the axial length of adistal leading segment 307 is minimized, so that the balloon 322 isrelatively close to the distal end of the steerable injector 300. Inthis embodiment, the plurality of transverse slots 308 are preferablyoccluded, to prevent inflation media from escaping into the centrallumen 316 or bone cement or other injectable media from escaping intothe balloon 322. Occlusion of the transverse slots 308 may beaccomplished in any of variety of ways, such as by positioning a thintubular membrane coaxially about the exterior surface of the tubularbody and heat shrinking or otherwise securing the membrane across theopenings. Any of a variety of heat shrinkable polymeric sleeves,comprising high density polyethylene or other materials, are well knownin the catheter arts. Alternatively, a tubular liner may be providedwithin the central lumen 316, to isolate the central lumen from thetransverse slots 308.

The balloon 322 is secured at a distal neck 309 to the leading segment307 as is understood in the balloon catheter arts. The distal neck 309may extend distally from the balloon, as illustrated, or may invert andextend proximally along the tubular body. In either event, the distalneck 309 of the balloon 322 is preferably provided with an annular seal324 either directly to the tubular body 301 or to a polymeric linerpositioned concentrically about the tubular body, depending upon theparticular device design. This will provide an isolated chamber withinballoon 322, which is in fluid communication with a proximal source ofinflation media by way of an inflation lumen 326.

In the illustrated embodiment, the balloon 322 is provided with anelongate tubular proximal neck which extends throughout the length ofthe steerable injector 300, to a proximal port or other site forconnection to a source of inflation media. This part can be blow moldedwithin a capture tube as is well understood in the balloon catheterarts, to produce a one piece configuration. Alternatively, the ballooncan be separately formed and bonded to a tubular sleeve. Duringassembly, the proximal neck or outer sleeve 328 may conveniently beproximally slipped over the tubular body 301, and secured thereto, aswill be appreciated by those of skill in the catheter manufacturingarts.

Referring to FIG. 16C, the inflation lumen 326 may occupy an annularspace between the outer sleeve 328 and the tubular body 301. This may beaccomplished by sizing the inside dimension of the outer sleeve 328slightly larger than the outside dimension of the tubular body 301, byan amount sufficient to enable the desired inflation flow rate as willbe understood in the art. Alternatively, referring to FIG. 16D, adiscrete inflation lumen 326 may be provided while the remainder of theouter sleeve 328 is bonded or snuggly fit against the tubular body 301.This may be accomplished by positioning an elongate mandrel (notillustrated) between the outer sleeve 328 and the tubular body 301, andheat shrinking or otherwise reducing the outer sleeve 328, thereafterremoving the mandrel to leave the discrete inflation lumen 326 in place.Alternatively, any of a variety of internal inflation lumen may bedevised, within the central lumen 316 of tubular body 301.

Referring to FIGS. 17A and 17B, there is illustrated an alternativeembodiment in which the distal aperture 314 is provided on a side wallof the tubular body. One or two or three or more distal apertures 314may be provided in any of the embodiments disclosed herein, dependingupon the desired clinical performance. In the illustrated embodiment,the distal aperture 314 is provided on the inside radius of curvature ofthe steerable section 306, as illustrated in FIG. 17B. The aperture 314may alternatively be provided on the opposite, outside radius ofcurvature, depending upon the desired clinical performance.

As a further alternative, the distal aperture or apertures 314 may beprovided in any of a variety of configurations on a distal cap or tip,adapted to be secured to the tubular body.

The steerable injection systems described above are preferably used inconjunction with a mixing and dispensing pump for use with amulti-component cement. In some embodiments, a cement dispensing pump isa hand-held device having an interface such as a tray or chamber forreceiving one or more cartridges. In one embodiment, the pump isconfigured to removably receive a double-barreled cartridge forsimultaneously dispensing first and second bone cement components. Thesystem additionally includes a mixing chamber, for mixing the componentssufficiently and reproducibly to fully automate the mixing anddispensing process within a closed system.

Bone cement components have conventionally been mixed, such as by hand,e.g., in mixing bowls in the operating room, which can be atime-consuming and unelegant process. The devices disclosed herein maybe used with conventional bone cement formulations, such as manuallymixed liquid-powder PMMA formulations. Alternatively, the use of aclosed mixing device such as a double-barreled dispensing pump asdisclosed herein is highly advantageous in reducing bone cementpreparation time, preventing escape of fumes or ingredients, ensuringthat premature cement curing does not occur (i.e., the components aremixed immediately prior to delivery into the body), and ensuringadequate mixing of components.

Two separate chambers contain respective materials to be mixed in aspecific ratio. Manual dispensing (e.g., rotating a knob or squeezing ahandle) forces both materials into a mixing nozzle, which may be aspiral mixing chamber within or in communication with a nozzle. In thespiral mixing nozzle, all or substantially all mixing preferably occursprior to the bone cement entering the steerable injection needle and,subsequently, into the vertebra. The cement dispensing hand pump may beattached to the steerable injection needle permanently, or removably viaa connector, such as slip-ring Luer fittings. A wide range of dispensingpumps can be modified for use with the present invention, includingdispensing pumps described in, for example, U.S. Pat. Nos. 5,184,757,5,535,922, 6,484,904, and Patent Publication No. 2007/0114248, all ofwhich are incorporated by reference in their entirety.

Currently favored bone cement compositions are normally stored as twoseparate components or precursors, for mixing at the clinical siteshortly prior to implantation. As has been described above, mixing ofthe bone cement components has traditionally been accomplished manually,such as by expressing the components into a mixing bowl in or near theoperating room. In accordance with the present invention, the bonecement components may be transmitted from their storage and/or shippingcontainers, into a mixing chamber, and into the patient, all within aclosed system. For this purpose, the system of the present inventionincludes at least one mixing chamber positioned in the flow path betweenthe bone cement component container and the distal opening on the bonecement injection needle. This permits uniform and automated orsemi-automated mixing of the bone cement precursors, within a closedsystem, and thus not exposing any of the components or the mixingprocess at the clinical site.

Thus, the mixing chamber may be formed as a part of the cartridge, maybe positioned downstream from the cartridge, such as in-between thecartridge and the proximal manifold on the injection needle, or withinthe proximal manifold on the injection needle or the injection needleitself, depending upon the desired performance of the device. The mixingchamber may be a discrete component which may be removably orpermanently coupled in series flow communication with the othercomponents of the invention, or may be integrally formed within any ofthe foregoing components.

In general, the mixing chamber includes an influent flow path foraccommodating at least two bone cement components. The first and secondincoming flow path are combined, and mixing structures for facilitatingmixing of the components are provided. This may include any of a varietyof structures, such as a helical flow path, baffles and or additionalturbulence inducing structures.

Tables 1-2 below depict the contents and concentrations of one exemplaryembodiment of bone cement precursors. Chambers 1A and 1B containprecursors for a first cement composition for distribution around theperiphery of the formed in place vertebral body implant with a higherparticle concentration to promote osteoinduction, as discussedpreviously in the application. Chambers 2A and 2B contain precursors fora second cement composition for expression more centrally within theimplanted mass within the vertebral body, for stability and crackarresting, as discussed previously in the application.

One of ordinary skill in the art will recognize that a wide variety ofchamber or cartridge configurations, and bone cements, can be used withthe present injection system. For example, in one embodiment, a firstcartridge includes pre-polymerized PMMA and a polymerization catalyst,while a second cartridge includes a liquid monomer of MMA as is commonwith some conventional bone cement formulations.

In some embodiments, the contents of two cartridges can be combined intoa single cartridge having multiple (e.g., four) chambers. Chambers maybe separated by a frangible membrane (e.g., 1A and 2A in a firstcartridge and 1B and 2B in a second cartridge, each component separatedby the frangible membrane or other pierceable or removable barrier). Inother embodiments, contents of the below cartridges can be manuallypre-mixed and loaded into the input port of the injection system withoutthe use of a cement mixing dispenser.

TABLE 1 Chamber 1A Methyl methacrylate (balance) Hydroquinone (~75ppm)(stabilizer) N,N-dimethyl-p-toluidine (~0.9%) Sterile bone particles(≧35 wt. %) (catalyst for polymerization) Barium sulfate (~20 wt.%)(radio- opacifier) Chamber 1B Benzoyl peroxide (~2%)(activatorPhysiological saline or poppy seed oil for polymerization) (balance)

TABLE 2 Chamber 2A Methyl methacrylate (balance) Hydroquinone (~75ppm)(stabilizer) N,N-dimethyl-p-toluidine (~0.9%) Sterile bone particles(~30 wt. %) (catalyst for polymerization) Barium sulfate (~20 wt.%)(radio- opacifier) Chamber 2B Benzoyl peroxide (~2%)(activatorPhysiological saline or poppy seed oil for polymerization) (balance)

As illustrated in FIGS. 18A and 18B, in one embodiment, a system or kitfor implanting bone cement includes at least some of the followingcomponents: a stylet configured to perforate a hole into the pedicle ofthe vertebral body; an introducer cannula 800 for providing an accesspathway to the treatment site, a steerable injection needle 700 todeliver bone cement to a desired location, and, a cement dispensing pump910 preferably configured to accommodate one or two or more dual chambercartridges 1200 as well as a mixing nozzle 995.

The stylet may have a diameter of between about 0.030″ to 0.300″, 0.050″to about 0.200″ and preferably about 0.100″ in some embodiments. Theintroducer cannula 800 is between about 8-14 gauge, preferably betweenabout 10-12 gauge, more preferably 11 gauge in some embodiments. Theintroducer cannula 800, which may be made of any appropriate material,such as stainless steel (e.g., 304 stainless steel) may have a maximumworking length of no more than about 12″, 8″, or 6″ in some embodiments.One or two or more bone cement cartridges, each having one or two ormore chambers, may also be provided. Various other details of thecomponents have been described above in the application.

One embodiment of a method for delivering bone cement into a vertebralbody is now described, and illustrated in FIGS. 19A-F. The methodinvolves the general concept of vertebroplasty and kyphoplasty in whicha collapsed or weakened vertebra is stabilized by injecting bone cementinto cancellous bone.

The cement implantation procedure is designed for uni-transpedicularaccess and generally requires either a local anesthetic orshort-duration general anesthetic for minimally invasive surgery. Oncethe area of the spine is anesthetized, as shown in FIGS. 19A-B, thephysician inserts a stylet 1302 to perforate a lumen 1304 into thepedicle wall 1300 of the vertebra 1308 to gain access to the interior ofthe vertebral body 1310. As illustrated in FIG. 19C, the introducercannula 800 is then inserted through the lumen 1304 for bone access aswell as acting as the guide for the steerable injection needle 700. Theintroducer cannula 800 is sized to allow physicians to performvertebroplasty or kyphoplasty on vertebrae with small pedicles 1300 suchas the thoracic vertebra (e.g., T5) as well as larger vertebrae. Inaddition, this system and method is advantageously designed to allowuni-transpedicular access as opposed to bi-pedicular access, resultingin a less invasive surgical procedure.

Once bone access has been achieved, as shown in FIG. 19C the steerableinjection needle 700 such as any of the devices described above can beinserted through the introducer cannula 800 and into the vertebra 1308.The entire interior 1310 of the target vertebral body may be accessedusing the steerable injection needle 800. The distal end 712 of theneedle 700 can be laterally deflected, rotated, and/or proximallyretracted or distally advanced to position the bone cement effluent portat any desired site as previously described in the application. Theradius can be adjusted by means of an adjustment control, such as a knobon the proximal end of the device as previously described.

The actual injection procedure may utilize either one or two basicsteps. In a one step procedure, a homogenous bone cement is introducedas is done in conventional vertebroplasty. The first step in the twostep injection involves injection of a small quantity of PMMA with morethan about 35%, e.g., 60% particles such as inorganic bone particlesonto the periphery of the treatment site, i.e., next to the corticalbone of the vertebral body as shown in FIG. 19D. This first cementcomposite 1312 begins to harden rather quickly, forming a firm but stillpliable shell, which is intended to minimize or prevent any bonemarrow/PMMA content from being ejected through any venules ormicro-fractures in the vertebral body wall. The second step in theprocedure involves an injection of a bolus of a second formulation ofPMMA with a smaller concentration such as approximately 30% inorganicbone particles (second cement composite 1314) to stabilize the remainderof the weakened, compressed cancellous bone, as illustrated in FIG. 19E.

Injection control for the first and second steps is provided by anapproximately 2 mm inside diameter flexible introducer cannula 800coupled to a bone cement injection pump (not shown) that is preferablyhand-operated. Two separate cartridges containing respective bone cementand inorganic bone particle concentrations that are mixed in the 60% and30% ratios are utilized to control inorganic bone particle to PMMAconcentrations. The amount of the injectate is under the direct controlof the surgeon or interventional radiologist by fluoroscopicobservation. The introducer cannula 800 is slowly withdrawn from thecancellous space as the bolus begins to harden, thus preventing bonemarrow/PMMA content from exiting the vertebral body 1308. The procedureconcludes with the surgical incision being closed, for example, withbone void filler 1306 as shown in FIG. 19F. Both the high and low bonecement particle concentration cement composites 1312, 1314 harden afterseveral minutes. In vitro and in vivo studies have shown that the 60%bone-particle impregnated bone cement hardens in 2-3 minutes and 30%bone-particle impregnated bone cement hardens between 4 to 10 minutes.

The foregoing method can alternatively be accomplished utilizing thecombination steerable needle of FIG. 16A, having a cavity formationstructure 320 thereon. Once the steerable injector 300 has beenpositioned as desired, such as either with deflection as illustrated inFIG. 19C, or linearly, the cavity forming element 320 is enlarged, suchas by introducing inflation media under pressure into the inflatableballoon 322. The cavity forming element 320 is thereafter reduced incross sectional configuration, such as by aspirating inflation mediafrom the inflatable balloon 322 to produce a cavity in the adjacentcancellous bone. The steerable injector 300 may thereafter by proximallywithdrawn by a small distance, to position the distal opening 314 incommunication with the newly formed cavity. Bone cement or other mediamay thereafter be infused into the cavity, as will be appreciated bythose skill in the art.

At any time in the process, whether utilizing an injection needle havinga cavity formation element or not, the steerable injector may beproximally withdrawn or distally advanced, rotated, and inclined to agreater degree or advanced into its linear configuration, and furtherdistally advanced or proximally retracted, to position the distalopening 314 at any desired site for infusion of additional bone cementor other media. More than one cavity, such as two, or three or more, maybe sequentially created using the cavity formation element, as will beappreciated by those of skill in the art.

The aforementioned bone cement implant procedure process eliminates theneed for the external mixing of PMMA powder with MMA monomer. Thismixing process sometimes entraps air in the dough, thus creatingporosity in the hardened PMMA in the cancellous bone area. These poresweaken the PMMA. Direct mixing and hardening of the PMMA using animplant procedure such as the above eliminates this porosity since noair is entrapped in the injectate. This, too, eliminates furtherweakening, loosening, or migration of the PMMA.

While described herein primarily in the context of vertebroplasty, oneof ordinary skill in the art will appreciate that the disclosedinjection system can be used or modified in a wide range of clinicalapplications, such as, for example, other orthopedic applications suchas kyphoplasty, treatment of any other bones, pulmonary, cardiovascular,gastrointestinal, gynecological, or genitourinary applications. Whilethis invention has been particularly shown and described with referencesto embodiments thereof, it will be understood by those skilled in theart that various changes in form and details may be made therein withoutdeparting from the scope of the invention. For all of the embodimentsdescribed above, the steps of the methods need not be performedsequentially and the individual components of the devices may becombined permanently or be designed for removable attachment at theclinical site.

1. A steerable vertebroplasty device, comprising: an elongate, tubularbody, having a first longitudinal axis, a proximal end, a distal end,and a central lumen, wherein the distal end comprises a deflectable zonedeflectable through an angular range and an exit port in communicationwith the central lumen; a handle on the proximal end of the tubularbody; an input port near the proximal end of the vertebroplasty device,in communication with the central lumen and configured to receive a bonefiller media; a deflection control on the handle operably attached to anaxially movable actuator that is operably attached to the tubular body,wherein the deflection control is configured to rotate, and wherein uponrotation of the deflection control in a first direction an axial forceis exerted on the movable actuator to change the curvature of thedeflectable zone of the tubular body; and a cavity creating elementconfigured to compact cancellous bone and carried by the deflectablezone; wherein the device is configured to be deflected using one-handedoperation, wherein the device further comprises an input port positioneddistally of the deflection control in communication with the centrallumen, wherein the input port is configured to receive a bone cement,wherein the input port has a second longitudinal axis that forms anangle with respect to the first longitudinal axis; wherein the tubularbody is substantially straight throughout its length from the input portto the exit port of the distal end in an unstressed state.
 2. Asteerable vertebroplasty device as in claim 1, wherein the cavitycreating element comprises an inflatable balloon.
 3. A steerablevertebroplasty device as in claim 2, wherein the inflatable balloon isdisposed proximally of the exit port on the tubular body.
 4. A steerablevertebroplasty device as in claim 1, wherein the length of the distaldeflectable zone is at least about 15% of the length of the tubularbody.
 5. A steerable vertebroplasty device as in claim 1, wherein thedeflection control is spaced proximally apart from a proximal end of thecentral lumen.
 6. A steerable vertebroplasty device as in claim 1,wherein the axially movable actuator comprises a pull wire operablyattached to the deflectable zone of the tubular body.
 7. A steerablevertebroplasty device as in claim 1, wherein the axially movableactuator is operably attached to an inner side wall of the tubular body.8. A steerable vertebroplasty device as in claim 1, wherein the axialforce comprises a proximally directed force.
 9. A steerablevertebroplasty device as in claim 1, wherein the deflection controlcomprises a dial.
 10. A steerable vertebroplasty device as in claim 1,wherein the deflection control allows for continuous adjustment of thecurvature of the deflectable zone of the tubular body.
 11. A steerablevertebroplasty device as in claim 1, wherein the deflection controlallows for discontinuous adjustment of the curvature of the deflectablezone of the tubular body.
 12. A steerable vertebroplasty device as inclaim 1, wherein the exit port is on a distal end of the deflectablezone.
 13. A steerable vertebroplasty device as in claim 1, wherein theexit port is on a sidewall of the deflectable zone.
 14. A steerablevertebroplasty device as in claim 1, wherein the first and secondlongitudinal axes are perpendicular to each other.
 15. A steerablevertebroplasty device as in claim 1, wherein the deflection control isrotatable about the first longitudinal axis.
 16. A steerablevertebroplasty device as in claim 1, wherein the input port comprises aluer connector.
 17. A steerable vertebroplasty device as in claim 1,further comprising a removable obturator for removably occluding theexit port.
 18. A method for treating a bone, comprising: creating apedicular access channel in a pedicle to access the interior of avertebral body; inserting an introducer cannula into the pedicle;inserting a steerable injection needle configured for single handoperation through the introducer cannula into the interior of avertebral body, the steerable injection needle having a proximal end, atubular body having a longitudinal axis, and a distal end, a control forcontrolling deflection of the distal end, and an input port having alongitudinal axis and configured to receive bone cement, wherein thecontrol is positioned proximally to the input port, wherein thelongitudinal axis of the input port is not coaxial with the longitudinalaxis of the tubular body, wherein the distal end has a firstconfiguration substantially coaxial with the longitudinal axis of thetubular body; adjusting the control to deflect the distal end of thesteerable injection needle to a second configuration that is notsubstantially coaxial with the longitudinal axis of the tubular body;and flowing bone cement through the steerable injection needle into theinterior of the vertebral body.
 19. The method of claim 18, furthercomprising the step of creating a cavity to compact cancellous bone ofthe vertebral body.